During his career he took several tropical medical study trips to India, East Asia, the West Indies, etc. He is especially known for his filarian research and as an instructor of tropical medicine classes in Hamburg.[1]

While working with dogs in Hamburg, he described "autoinfection" and discovered the migratory route taken by the parasite Strongyloides stercoralis prior to ending up in the intestine.[3] The term "Fülleborn's method" is a procedure for examining parasitic ova in faecal matter.

Das deutsche Njassa- und Ruwuma-gebiet, land und leute, nebst bemerkungen über die Schire-Länder. : Mit benutzung von ergebnissen der Njassa- und Kingagebirgs-expedition der Hermann und Elise geb. Heckmann Wentzel-stiftung (1906) – The German Nyassa and Ruwuma region, the country and its people; along with remarks on the Shire-regions: written with the use of results from the Nyassa and Kinga Mountains expedition of the Hermann and Elise Heckmann (née Wentzel) Foundation.